1. Field of the Invention
The present invention relates to a filter device and more particularly to a hollow fiber filter device used to filter liquid in which minute particles are suspended, for example return water (condensate recycled) in a nuclear power plant.
2. Description of the Related Art
In the conventional hollow fiber module for use in a filter, a plurality of hollow fibers are formed in a bundle and an upper end of the bundle is secured to a horizontal plate within the filter casing so that each fiber is open at the upper end while being closed at the lower end with a filling material inserted at that end or with two opposite ends thereof being open and positioned at the upper portion in such a manner that the overall configuration thereof is U-shaped. Thus, the construction of such a module has been achieved by securing one end of the bundle to a solid member while leaving the opposite end free so that the module may be handled by the solid member. In such a module as described above, some drawbacks have been encountered stemming from the free state of one end of the module, so a module for restraining the movement of the lower end of the bundle was devised as disclosed, for example, in copending U.S. application Ser. No. 868,050.
Consideration has also been given to increasing the filtering capacity of the module by making the length of the module longer so that the filtering capacity relative to the installation area of the filterring device may be improved.
However, it has been found that the capacity of the filtering device cannot be increased to the extent expected by lengthening the fiber module and mere lengthening of the module was in practice found to be relatively useless.
Accordingly, it has been desired to increase the filtering capacity with respect to a limited installation area.